Gas phase analytical methods depend upon gas chromatography for separation purposes, mass spectrometry for purposes of identification and quantification, and computer science for instrument operation, data acquisition and data analysis. Two major advances have been made recently. These are the development of high resolution thermostable glass open tubular capillary columns for gas chromatography, and the establishment of atmospheric pressure ionization (API) mass spectrometry. The work proposed for next year is to combine these developments, with advances in computer technology, to form a GC-MS-COM system of unparalleled capabilities in separation and sensitivity of detection, and to use the system in human studies of metabolic problems.